1. Field of the Invention
This invention relates to techniques of granulating of pharmaceuticals and food-stuffs, etc., spherically or centrifugal tumbling granulating and coating for applying coating to spherical granules.
2. Statement of the Related Art
A centrifugal tumbling granulating-coating apparatus (hereinafter referred to as a "CF apparatus") as being an apparatus for applying coating to spherical granules are widely put on the market as being represented by a centrifugal tumbling coating-granulating apparatus, "CF-GRANULATOR manufactured by Freund Industrial Co., Ltd", for example. The construction of this CF apparatus is like one shown in FIG. 3. Originally, the CF apparatuses have been developed to make coating of tablets and the like as its main use. However, by now, the spherically granulating and coating of pharmaceutical layers onto the surfaces of the spherical granules have become the main uses.
In these uses, it is required to produce in high yield the spherical granules which are satisfactory in roundness within a predetermined range of grain size, and to provide uniform coating layers onto the spherical granules. Then, in order to satisfy these requirements, there have heretofore been made various proposals on the construction and shape of the CF apparatuses.
That is, for example, the followings are known as the CF apparatuses suitable for coating of the tablets and the like. According to "a coating method and an apparatus therefor" described in Japanese Patent Publication No. 46-22544, as shown in FIG. 4, there is known a coating pan 27 including a rotary disk for being rotated horizontally at a central portion, a curved surface portion 25 provided around this rotary disk 24 and a cylindrical portion 26 connected to the curved surface portion 25. According to "a coating method and an apparatus therefor" described in Japanese Patent Publication No. 46-10878, as shown in FIG. 5, there is known a coating pan 37 including a rotary disk 34 for being rotated horizontally and a curved surface fixed wall 35.
According to "an automatic coating apparatus for particles" described in Japanese Patent Publication No. 54-992, as shown in FIG. 6, there is disclosed an automatic particle coating apparatus 47, in which moisture in the coating apparatus is measured by a moisture detector, whereby the feeding speed of a binder and hot air for drying are controlled. Furthermore, according to "compression molding and granulation of pharmaceuticals" as being a thesis presented for a degree to the Tohoku University by Mr. Yoshiro Funakoshi, as shown in FIG. 7, a centrifugal tumbling coating apparatus 57, in which a fixed wall 55 is in curved inwardly.
The inventors of the present invention have found that, although these CF apparatuses, particularly those being sold in the market at present, are suitable for coating the tablets and the like and for processing the spherical granules and the like, further improvements are necessary to better performance.
That is, the capacity of processing the powder or granular material in the standard CF apparatuses sold in the market at present is set at 30.about.50 kg/batch on the basis of the finished product, i.e. the apparatuses having a diameter of the rotary disk of 1,000 mm, in the case in which the powder or granular material more than this amount is charged, the powder or granular material cannot be tumbled satisfactorily, whereby the particles having satisfactory roundness cannot be produced. The limit of the processing capacity in these CF apparatuses has been put up with as an inevitable characteristics of the CF apparatuses.
Recently, in pharmaceutical manufactures, a size of a drug-manufacturing apparatus has being large so that the production per batch may be increased, corresponding thereto, to increase the production per batch of the CF is demanded. Here, in order to satisfy this requirement, as far as the shape of the CF apparatuses is not changed, it is necessary to provide further large-sized CF apparatuses.
However, in the CF apparatus, it is required to hold a slit width between a side wall and the rotary disk to be narrow in order to prevent the powder or granular material on the rotary disk from dropping, so that it is very difficult to make the apparatuses be large-sized in view of the accuracy of manufacturing. Then, at present, while the high costs and the increased installation area are put up with, a multitude of the CF apparatuses are provided, whereby pharmaceutical manufactures has been corresponding to increase in the manufacturing capability.
The inventors of the present invention have analyzed the conventional CF apparatuses from the viewpoint of that the limit of the above-described processing capacity may be cleared by effectively acting the centrifugal force for tumbling the powder or granular material on each of the particles. As the result, it has been found that, under the shapes of the CF apparatuses which have been known by now, the centrifugal force cannot be satisfactorily acted on the particles. For example, in a CF apparatus 67 being put on the market at present as shown in FIG. 3, the peripheral edge portion of a rotary disk 64 and a side wall are continuous with each other with a slightly clearance, and a radius of curvature of the continuous part thereof is small, friction loss of energy is therefore increased when the powder or granular material, which has received centrifugal force, is tumbled in the vertical direction and the tumbling action on a fixed wall is decreased, thereby restricting the upper limit of a charged volume. Furthermore, in apparatuses 27, 37 and 47 as described in the documents shown in FIGS. 4 through 7, the radii of curvature of connecting portions are large, however, rotary disks 24, 34 and 44 do not reach the vertical portions of inner walls, so that satisfactory centrifugal force cannot be obtained (FIGS. 4 to 6), or, the inner walls are curved inwardly, whereby surplus resistance is generated, so that the centrifugal force is reduced (FIG. 5 and 7). The productivity in the prior art is therefore low.